1. Field of the Invention
The present invention relates to a method of scanning an optical disk, and an apparatus therefor.
2. Description of the Related Art
Disk apparatuses known in the art include one capable of recording digital data or digital images, speeches, systems or similar data in magnet-optical disks or optical disks including phase change disks. For this type of disk apparatus, a recording system implementing both high density recording and high speed search at the same time with a single head is desirable. Today, a CAV recording system, a CLV recording system and an MCAV recording system are available with an optical disk type disk drive which records digital data or video and audio data in optical disks.
The CAV system records data in an optical disk while causing it to spin at a constant speed. This system realizes high speed search without regard to a head device because the rotation speed is constant. In addition, the system implements the simultaneous reproduction of different positions at the time of recording and simplifies a spindle servo. However, this system is not feasible for high density recording because the shortest record wavelength is determined by the innermost circumference.
The CLV featuring a constant linear velocity maintains the relative velocity constant over the entire area of a disk and therefore maintains the record wavelength constant. This kind of system is feasible for high density recording. However, because the rotation speed of the disk varies in accordance with the position of a head, the system is not feasible for high speed search. Further, the system cannot implement the simultaneous reproduction of different positions and needs a sophisticated spindle servo.
The MCAV system, integrating the merits of the CAV and CLV systems, maintains the rotation speed of a disk constant and increases the amount of data for a track in proportion to the radius of the disk. Because the rotation speed is constant, the record bit rate is increased in proportion to the radius of a disk (variable clock recording and variable clock reproduction). This kind of system is capable of effecting high speed search because the record wavelength is constant over the entire area of a disk and because the number of disk rotation data is constant. Further, the system is capable of reproducing different positions at the same time during recording and simplifying a spindle servo.
A system of the type recording data by using both the land portions and groove portions of disk tracks, i.e., a so-called land/groove recording system is also available although it is different from a recording system. The land/groove recording system doubles the recording density particular to conventional land recording or groove recording and thereby increases the recording time. Thereby, by combining the MCAV system and land/groove recording system, it is possible to realize high density and advanced function at the same time.
FIG. 12 shows how a head scans a disk in the combined MCAV and land/groove recording system. FIG. 13 shows the order of data (corresponding to frames which will be described) actually scanned. As shown in FIG. 12, a head repeatedly jumps one track backward from a land track portion to a groove portion, or vice versa. As a result, the data shown in FIG. 13 are sequentially recorded in a disk. In FIG. 13, the numerals indicate, e.g., the frame numbers of a moving picture. This allows, e.g., a moving picture to be continuously recorded in both the land portion and groove portion of a disk.
However, the above conventional recording system has a problem that the jump from a land portion to a groove portion and the jump from a groove portion to a land portion are not practicable without resorting to complicated adjustment. Another problem is that because the two different kinds of track jumps are replaced every track, an amplifier gain, among others, must be switched at a high speed. It is therefore extremely difficult to realize stable track jumps.
Japanese Patent Laid-Open Publication No. 7-282855 proposes an arrangement for implementing a rapid jump from a land track to a groove track. However, the arrangement taught in this document is too sophisticated in configuration to be practiced.